The present invention relates to methods and apparatuses for absorbing impact from structures, more particularly to such methods and apparatuses which are implemented at berthing locations for absorbing impact from marine vessels.
xe2x80x9cFendersxe2x80x9d are bumpers which are utilized at docks, wharves, piers, moorages and anchorages for absorbing kinetic energy of berthing marine vessels. A fender absorbs kinetic energy of the berthing vessel by converting the kinetic energy into potential energy in the fender material system.
Fender systems have been used, or considered for use, wherein the potential energy is realized essentially in at least one of the following forms: deflection of a fender pile; compression of a rubber, fender component; deformation of a foam-filled fender; torsion of a fender""s cylindrical shaft; pressurization of a pneumatic fender; fluid motion/pressurization of a hydraulic fender.
Foam-filled fenders generally comprise a resilient, closed-cell foam wrapped with an elastomeric skin. The cellular structure of the foam reacts like individual pneumatic fenders by absorbing energy through deformation. The foam-filled fenders have high energy absorbing capabilities with relatively small reaction force and can float with the tide, handling several surface ship types. Since foam-filled fenders are typically large, they can act as a separator and provide a good standoff.
The U.S. Navy is currently utilizing composite materials in the fabrication of foam-filled fenders for berthing ships. The current design of a foam-filled fender for U.S. Naval ships includes a cylinder having a urethane foam core, overwraps of nylon, and a urethane sprayed over the cylindrical surface. The U.S. Navy""s foam-filled fender system has demonstrated effectiveness in terms of reacting certain kinds of ship loads against piers, but has yet to be engineered for generic applications.
The U.S. Naval fenders currently in use are fabricated for a particular class of ship. U.S. Naval vessels which are characterized by different displacements require different fenders to be employed; one reason for this has been the U.S. Navy""s need to ensure that a particular U.S. Naval ship""s hull loading is maintained below a specific level. Furthermore, fenders of current U.S. Naval design are fixed in terms of the amount of energy which can be reacted. In order to absorb more energy, more or larger current U.S. Naval fenders are required.
Although the U.S. Navy""s current foam-filled fender design has been successful in certain modes of practice, it does not lend itself to an analytical design methodology using current design tools. The method for fabricating the U.S. Navy""s current foam-filled fender includes wrapping a urethane foam core with nylon fiber, and spraying urethane onto the fiber as it is wound onto the urethane core material; this technique results in operator-to-operator variance in urethane coating thickness or fiber volume fraction.
Accordingly, the mechanism of energy absorption cannot be accurately modeled for current U.S. Navy foam-filled fender systems. The efficacy of a given U.S. Navy foam-filled fender for a particular application requires independent empirical verification. Due to this incapability of advance fender design, the U.S. Navy""s current foam-filled fender system necessarily lacks the versatility to predictably adapt to various configurations of marine vessel and/or berth.
Current U.S. Navy fenders are experiencing significant design overloads and are being replaced at an annual cost of millions of dollars per year. Moreover, many pier structures owned by the U.S. Navy and other entities are decrepit or dilapidated. Aging or deteriorating pier structures require renewed analysis to account for degrading mechanical properties. If analytical procedures are not soon established, existing pier structures may be prematurely replaced.
In view of the foregoing, it is an object of the present invention to provide a bumper/fender system which can be used effectively for absorbing impact of a variety of marine vessels at a variety of berthing stations.
Another object of the present invention is to provide such a bumper/fender system which can be thus used for both large and small marine vessels.
It is a further object of this invention to provide such a bumper/fender system which admits of analytical modeling for purposes of predicting such varied usage.
A further object of this invention is to provide such a bumper/fender system which is economical.
The present invention is, to some extent, a xe2x80x9cvariation on a themexe2x80x9d disclosed by Crane et al. at the aforementioned U.S. Pat. No. 6,053,664 which is incorporated herein by reference. The invention disclosed by Crane et al. at U.S. Pat. No. 6,053,664 (hereinafter referred to as xe2x80x9cCrane et al. ""664xe2x80x9d) was developed as part of Phase I of an SBIR (xe2x80x9cSmall Business Innovation Research Programxe2x80x9d) project (OSD95-016). The present invention was developed as part of Phase II of the same SBIR project (OSD95-016). However the present invention represents an inventive improvement vis-a-vis"" Crane et al. ""664, and may be preferable thereto in many practical contexts.
Like the invention disclosed by Crane et al. ""664, the present invention provides a system for absorbing the impact of a relatively moving body. Also like the invention disclosed by Crane et al. ""664, the present inventive system comprises a xe2x80x9cbumperxe2x80x9d which includes fiber-reinforced high strain-to-failure viscoelastic matrix material. Further like the invention disclosed by Crane et al. ""664, the bumper is disposed in suspended fashion, either hanging or floating. Again like the invention disclosed by Crane et al. ""664, upon impact by the relatively moving body the bumper reacts so as to strike against a closely situated structural entity.
Unlike the invention disclosed by Crane et al. ""664, the present invention implements a xe2x80x9csmart valvexe2x80x9d for the bumper. Furthermore, unlike the invention disclosed by Crane et al. ""664, the present invention obviates the need for one or more xe2x80x9cdeformersxe2x80x9d for receiving the bumper after the bumper initially receives the body, energy is dissipated in a different manner. The present invention""s bumper can react against any relatively rigid structural surface (such as a hard solid wall-like structure) which is part of any stable structure, such as a pier, dock, wharf, edifice, etc.
The present invention uniquely features a xe2x80x9csmartxe2x80x9d valve methodology which optimizes the load displacement curve of the inventive fender. The present invention also uniquely features utilization of a reusable winding mandrel in the fabrication of many embodiments of the inventive fender. In the light of the instant disclosure and the disclosure by Crane et al. ""664, the ordinarily skilled artisan will appreciate the substantial extent of applicability to the present invention of the teachings and principles according to Crane et al. ""664, as well as the significant differences therebetween.
To elaborate, the inventive system according to many embodiments of Crane et al. ""664 comprises at least two composite structures and at least one housing. Each composite structure includes fiber-reinforced high strain-to-failure viscoelastic matrix material. At least one composite structure is a bumper (e.g., a xe2x80x9ccylindroidxe2x80x9d bumper which includes a hollow cylindrical axially intermediate portion and two protuberant axially extreme portions) for initially receiving the body. At least one composite structure is a deformer (e.g., a xe2x80x9ctension tubexe2x80x9d) for consequently receiving a bumper. Each housing is for securing at least one deformer and for suspending at least one bumper. Each bumper is situated adjacent at least one deformer. A cylindroid bumper, for instance, can be disposed horizontally, vertically or obliquely.
The inventive system in accordance with the present invention is markedly distinguishable from the inventive system in accordance with Crane et al. ""664. In accordance with many presently inventive embodiments, an energy-absorbing system comprises: a structure; fluid contained by the structure; movement-restrictive situation means for the structure; valvular means for permitting escape of the fluid; actuator means for adjusting the valvular means; control means for the actuator means; and, pressure sensing means for informing the control means.
Typically according to this inventive energy-absorbing system, the valvular means is closed prior to a collision between a body and the structure. During the collision the valvular means operates in four stages, the four stages consisting of: (i) a first stage wherein the valvular means remains closed; (ii) a second stage wherein, when pressure is approximately maximal, the valvular means opens; (iii) a third stage wherein, when pressure commences to drop, the valvular means remains open so as to adaptively sustain, on an ongoing basis, an approximately steady force associated with the collision; and, (iv) a fourth stage wherein, when pressure approaches zero, the valvular means closes.
During the first stage, the valvular means is in statically closed mode; the pressure (against the bumper) is increasing from zero. During the second stage, the valvular means is in statically open mode; the pressure is approximately plateauing at about the maximal value. During the third stage, the valvular means is in dynamically open mode; the pressure is decreasing, while the force is approximately plateauing at about its value existing when the pressure commences to decrease at the outset of the third stage. During the fourth stage, the valvular means returns to statically closed mode; the pressure and the force each decrease steeply or precipitously, to or toward zero.
According to many inventive embodiments, especially those involving marine docking applications, the present inventive system for absorbing impact comprises: a bumper for being subjected to impact, wherein the bumper has an interior space and includes fiber-reinforced high strain-to-failure viscoelastic matrix material; means for suspending the bumper; a structure for restraining the bumper when said bumper is subjected to said impact; fluid (liquid or gas) which at least substantially fills the interior space; an outlet valve which regulates the flow of the fluid from the interior space; at least one pressure sensor (e.g., pressure transducer) which sends an electrical output signal relating to the pressure with respect to the wall of the bumper; a processor-controller which receives the electrical output signal and sends an electrical control signal in accordance with the electrical output signal, wherein the processor-controller has a memory containing information for determining, based on the pressure, whether and how the outlet valve should be actuated; and, a servo valve which receives the electrical control signal, wherein the servo valve actuates the outlet valve in accordance with the electrical control signal.
Each pressure sensor measures pressure and relays corresponding pressure information to the processor. The processor is typically implemented as a xe2x80x9cprocessor-controllerxe2x80x9d which monitors sensory signals and conveys corresponding control signals in a feedback control system. The servo valve is typically rendered xe2x80x9csmartxe2x80x9d by means of a continual feedback loop wherein: Each pressure sensor sends to the processor-controller a sensor signal which is dependent upon the pressure of the bumper; in turn, the processor-controller (which includes algorithmic software for governing its reaction to the sensor output signal received) sends to the servo valve a control signal which is dependent upon the sensor signal(s) received from the pressure sensor(s). Depending upon the control signal received from the processor-controller, the servo valve actuates, or refrains from actuating, the outlet valve (which serves as a pressure relief valve).
For some embodiments of the present invention, xe2x80x9cactuationxe2x80x9d by the servo valve entails causing the initially completely closed outlet valve to regulatively variably open; that is, subsequent to commencement of the impact and upon receipt of the control signal corresponding to the attainment of predetermined conditions related to the pressure (against the bumper wall), the servo valve causes the outlet valve to open correspondingly in terms of extent or proportion. However, it is preferred for most inventive embodiments that xe2x80x9cactuationxe2x80x9d by the servo valve not only entail causing (permitting) the outlet valve to initially then adjustingly open, but also entail causing (permitting) the outlet valve to finally and completely close anew, all in correspondence with attainment of predetermined conditions. The final, complete closure of the outlet valve reduces or prevents a so-called xe2x80x9creboundxe2x80x9d effect.
Subsequent to commencement of the impact, upon receipt of the control signal corresponding to the attainment of a first predetermined condition related to the pressure (i.e., pressure is at about a maximum value), the servo valve allows the outlet valve to open (i.e., move to an open position); the pressure remains at the maximum value until it begins to drop. Then, upon receipt of the control signal corresponding to the attainment of a second predetermined condition related to the pressure (i.e., pressure is beginning to drop from the maximum value), the servo valve allows the outlet valve to move, remaining open in such a manner as to approximately maintain constancy of the reaction force associated with the impact; depending on the position of the butterfly valve core along the axial translation of the outlet valve, this movement of the butterfly valve core can result in either an increase in the flow of water through the outlet valve, or a decrease in the flow of water through the outlet valve. Then, upon receipt of the control signal corresponding to the attainment of a third predetermined condition related to the pressure (i.e., pressure abruptly drops, approaching zero, said abrupt drop corresponding to cessation or near cessation of motion of the object which impacts the bumper), the servo valve allows the outlet valve to close (i.e., move to the closed position).
The servo valve (which controls the position of the outlet valve) is typically an electromechanical device such as a solenoid valve or an electronically-controlled actuator. For many inventive embodiments the servo valve is a solenoid valve which comprises a solenoid and a pneumatic actuator. The pneumatic actuator actuates with compressed air which is controlled by the solenoid. When the processor sends the appropriate signal to the solenoid, the solenoid causes the pneumatic actuator to be actuated, which in turn allows the outlet valve to move (e.g., move in the xe2x80x9copenxe2x80x9d direction) or close (e.g., move in the xe2x80x9cclosedxe2x80x9d direction). Depending upon the position of the butterfly valve along the axial translation of the valve, the rate of flow of water will vary, thereby controlling the pressure in and on the fender.
For some embodiments of the present invention, the servo valve is an electronically-controlled actuator; that is, xe2x80x9copeningxe2x80x9d and xe2x80x9cclosingxe2x80x9d of the outlet valve is achieved by means of an electronically-controlled actuator, rather than by means of the combination of a pneumatic actuator with a solenoid. When the processor sends the appropriate signal to the electronically-controlled actuator, it causes the outlet valve to vary its position.
In inventive practice, the ordinarily skilled artisan is aware that an electronically-controlled actuator and a pneumatic actuator-with-solenoid combination are two alternative means for varying the position of the outlet valve (in other words, xe2x80x9copeningxe2x80x9d and xe2x80x9cclosingxe2x80x9d the outlet valve), and is acquainted with methods and techniques for effectuating each. The person of ordinary skill in the art is familiar with commercially available electronically-controlled actuators which may be suitably implemented, as well as with commercially available pneumatic actuators and solenoids which may be suitably implemented in combination. Depending upon the particular inventive embodiment practiced, a pneumatic actuator may prove to be slightly more responsive than an electronic actuator, or vice versa; nevertheless, neither approach to inventively practicing the servo valve can necessarily be recommended over the other.
In typical inventive practice, the bumper includes an axially symmetrical cylindroid structural wall which surrounds an interior space (e.g., cavity or hollow). The cylindroid structural wall includes a cylindrical axially intermediate portion and two protuberant axial end portions which are rounded or tapered (e.g., convexo-concave). The outlet valve is typically situated in the vicinity of the extreme axial end of the cylindroid bumper, approximately coincident with the imaginary axis of the bumper. Some inventive embodiments provide a plurality of outlet valves (thus perhaps requiring plural servo valves); for instance, two outlet valves can be provided for a cylindroid bumper wherein each outlet valve is oppositely situated at an extreme axial end.
For purposes of receiving the anticipated impact, the cylindroid bumper can be disposed any which wayxe2x80x94horizontally, vertically or obliquelyxe2x80x94typically so that its axis of symmetry lies in a vertical plane which is generally directed so as to face or meet the anticipated impacting entity (such as a ship which is berthing). Preferably, the fluid which fills or substantially fills the cavity is liquid rather than gaseous. In testing conducted by the U.S. Navy, water was the liquid of choice. According to this invention, the composite bumper structure can contain a fluid, either gaseous (e.g., air) or liquid (e.g., water); however, in inventive practice, since a liquid (as compared with a gas) better lends itself to regulation of pressurization and to control of fluid motion, liquidity of the bumper""s fluid contents is generally preferable to gaseousness thereof.
Many embodiments of the present inventive system are xe2x80x9cself-containedxe2x80x9d in the sense that all the components are joined with or integrated with the bumper. The pressure sensor(s) and the outlet valve(s) are in engagement with the bumper""s structural wall. The servo valve(s) and the processor-controller means (such as one or more microprocessors, each of which is small enough to fit) may be each contained within the bumper""s cavity (inside the bumper""s structural wall), or either or both may be external to the bumper""s cavity; preferably, the servo valve and the processor are in relatively close proximity.
Conventional bumper systems are dependent upon adaptation of size and/or number of fenders in order to suit different marine vessels in terms of energy absorption; by comparison, the inventively xe2x80x9csmartxe2x80x9d bumper system is readily adaptable to diverse marine vessels. Fenders currently utilized for U.S. Navy vehicles are fabricated for a particular class of ship. Vessels with different displacements require different fenders to be employed. One reason for this is to ensure that the hull loading is kept below a specific level. Also, the energy that can be reacted by the U.S. Navy""s current design is fixed; that is, to absorb more energy, more or larger fenders are required.
By contrast, the inventive xe2x80x9csmartnessxe2x80x9d attribute endows an inventive fender with sufficient versatility and universality for utilization in connection with varieties of marine vessels and berthing stations. The inventive fender can readily be tailored and analyzed particularly in terms of its xe2x80x9csmartness.xe2x80x9d The inventive fender system is susceptible of analysis using conventional techniques and is tailorable to numerous pier configurations as well as to numerous types and sizes of ships and other marine vessels. The present invention permits anticipatory tailoring of fenders for desired applications so as to avoid overpressurization on the prospectively impacting marine vessel hulls.
In accordance with many embodiments of the present invention, an apparatus comprises a machine having a memory. The machine contains a data representation pertaining to the impact of an object upon a fluid-filled bumper for being subjected to the impact. The data representation is generated during the impact, for availability for containment by the machine, by the method comprising: receiving an electrical output signal from at least one pressure sensor, the electrical output signal pertaining to the pressure of said bumper; based on the electrical output signal, estimating the mass and the velocity of the object; and based on the estimated mass and velocity, establishing an electrical control signal for controlling the degree of actuation of an outlet valve which regulates the flow of the fluid from the bumper.
Many inventive embodiments provide energy-dissipating apparatus comprising a bumper, at least one variable valve, at least one sensor and a computer. The bumper has a cavity and contains fluid in the cavity. The at least one variable valve is for variably releasing the fluid from the bumper. The bumper has an elastomeric quality and is adaptable to situation so that the variably releasing can affect the velocity of an object which collides with the bumper. The at least one sensor is for sensing the pressure in relation to said bumper. The computer is in communication with the at least one variable valve and with the at least one sensor. The computer is capable of controlling the variably releasing of the fluid from the bumper, whereby the velocity is associated with an earlier period of approximate constancy of a pressure value in relation to the colliding, and whereby the velocity is associated with a later period of approximately constancy of a force value in relation to the colliding. The earlier period is approximately coincident with an approximate increasing tendency in the force value. The later period is approximately coincident with an approximate decreasing tendency in the pressure value below the pressure value existing in the earlier period.
Also according to many embodiments of this invention, a computer program product comprises a computer useable medium having computer program logic recorded thereon for enabling a computer to variably control the valvular release of fluid from a bumper. The computer program logic comprises: in anticipation of the object colliding with the bumper, means for enabling the computer to define a maximum pressure value relating to the colliding; while the object collides with the bumper, means for enabling the computer to periodically obtain sensed pressure values relating to the colliding, the sensed pressure values deriving from at least one sensor for sensing the pressure in relation to the bumper; while the object collides with the bumper, means for enabling the computer, based on the sensed pressure values, to compute force values relating to the colliding; and, while the object collides with the bumper, means for enabling the computer, based on the maximum pressure value, the sensed pressure values and the computed force values, to compute control values corresponding to the valvular release.
The inventive bumper system is versatile especially in that the xe2x80x9csmartxe2x80x9d aspect thereof lends itself to broad applicability to a variety of marine vessels. The inventive xe2x80x9csmartxe2x80x9d valve arrangement can be varied to apply to different maximum hull pressures while maintaining the optimum load stroke curve for maximum energy dissipation. A marine vessel""s contact region can be designed to keep the hull loading below a specific threshold value. In addition, the xe2x80x9csmartxe2x80x9d valve can determine when the ship velocity is zero, whereupon the outlet valve closes completely, thereby eliminating any rebound typically experienced with conventional fender design.
Moreover, the materials utilized for the present invention have demonstrated long term durability in sea water environments, and therefore should be capable of greater longevity than are the fenders which are currently being used. Furthermore, the capability of the inventive fender system to allow for higher berthing speeds without overloading either pier structures or ship hulls will greatly benefit both U.S. Naval and commercial shipping. Commercially, for both container traffic and ferry traffic, the increased berthing speeds will result in shorter times for off-loading and on-loading. Shorter turn-around times will result in lower shipping costs.
Iincorporated herein by reference is the following report which was issued pursuant to SBIR contract between the U.S. Navy and xe2x80x9cperforming organizationxe2x80x9d Production Products Manufacturing and Sales Company, Inc., 1285 Dunn Road, St. Louis, Mo.: Elastomeric Composite Bumpers, Second Quarterly Progress Report, May 19, 1997 thru Aug. 18, 1997, sponsored by the Office of Naval Research (ONR), Contract No. N00014-97-C-0117, Contract Effective Date Feb. 18, 1997, Contract Expiration Date Feb. 18, 1999; xe2x80x9cDistribution authorized to U.S. Government agencies only; report contains proprietary data produced under SBIR contract. Other requests shall be referred to the performing organization listed above.xe2x80x9d This report includes pages 1 through 27 plus its xe2x80x9cAppendix Axe2x80x9d (commencing at page 28) which includes pages C-1 through C-8, D-1 through D-7 and I-1 through I-2.
Other objects, advantages and features of this invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.